This invention relates generally to voltage transformers and to microwave devices and more particularly to high-frequency transformers for microwave cookers or ovens. More specifically the invention relates to a high-frequency transformer for a microwave oven in which transformer short-circuiting between the windings of the primary coil and the secondary coil is positively prevented.
In general, a microwave cooker or oven for cooking by heating materials to be cooked is provided with a built-in magnetron, to which high-frequency power from a step-up transformer is supplied through a rectifier. A step-up transformer of this type has a primary winding connected to a commercial power supply and a secondary winding connected to the magnetron side, which windings are wound on a common coil bobbin (for example, as described in Japanese Patent Publication No. 3636/1981 and Utility Model Publication No. 32733/1976). Although ample electrical insulation is originally provided between these primary and secondary windings at the time of manufacture, the electrical insulation layer ruptures and causes short-circuiting in some cases after use over a long period at a high potential difference.